The present invention relates to a biometric measuring device having a shape similar to that of a wristwatch and capable of optically measuring biometric information, such as pulse rate, and more particularly, the present invention relates to an improved band for fixing the device to a living body.
In order to obtain information, such as pulse rate, from a living body, a technique for applying light on the living body and measuring fluctuations of reflected light has already been put into practice. Techniques for pressing and fixing an optically-measuring sensor unit to a surface of a living body, such as a finger surface or a wrist surface, include a technique disclosed in Japanese Unexamined Patent Publication No. 9-108191, which is an application of the present inventors. According to this technique, a circumferentially elastic single supporter-like band is used. This technique is suitable for fixing a sensor unit of small size to a human fingertip.
However, the above-described technique has the following problems.
First, when a sensor unit larger than a sensor unit that can be fitted on a finger, is attached to, for example, a wrist, a large force for holding the weight of the sensor is required for a band. In particular, when an optical sensor unit is used, in order to prevent measurement errors caused by external light, high adherence is required so that a gap is not formed between the sensor unit and the surface of the living body.
In addition, at an easily twisted site, such as a wrist, since a gap is particularly easy to form between the sensor unit and the surface of the living body, the holding force required is excessive. For this reason, the force for pressing the living body must be necessarily increased. This allows the living body to feel high sensation of pressure, and it is therefore difficult to use such a sensor unit for a long time.
The present invention was achieved in consideration of the foregoing circumstances, and an object thereof is to provide a biometric measuring device capable of being mounted on a measurement site of a living body with high adhesion while minimizing the sensation of pressure.
A biometric measuring device according to the present invention includes a light-emitting means (or light-emitting body) for applying light to a living body; a biometric information detection means (or light-receiving body) for receiving reflected light from the living body of the light applied by the light-emitting means (or light-emitting body) to produce a biometric information signal according to the amount of light received; a support body for supporting the light-emitting means (or light-emitting body) and the biometric information detection means (or light-receiving body); and a band connected to the support body and wound around the living body near the detection site to fix the support body to the living body. Further, according to the present invention, the band is formed of a circumferentially flexible material, and flexibility thereof partially varies in the circumferential direction. In the device according to the present invention, movement, such as twisting of a living body, is permitted by a portion of the band having high flexibility, and holding ability against the living body can be secured by a portion having low flexibility. Therefore, it is possible to mount the device on a measurement site of a living body with high adhesion while minimizing sensation of pressure, and measuring accuracy of the biometric measuring device is improved.
In addition, according to the present invention, the band may have a base material wound around the living body; and an elastic member disposed inside of the base material and having the flexibility higher than that of the base material.
In this case, the base material of the band is wound around the living body together with the support body, whereby the device is mounted on the living body. The holding ability against the living body can be secured by the base material having low flexibility and at the same time, movement, such as twisting of the living body can be permitted by the elastic member disposed inside the base material. Therefore, it is possible to mount the device on the measurement site of the living body with high adhesion while minimizing sensation of pressure, and measuring accuracy of the biometric measuring device is improved.